The use of light activated drugs is a very attractive option for the development of therapeutic methodologies that minimize damage to normal tissue by allowing spatial and temporal control over toxicity. Light activated drugs have been used for blood sterilization. For example, U.S. Pat. No. 6,030,767 (Wagner et al.) describes photosterilizing blood and blood components, such as red blood cells or plasma, using methylene blue derivatives. See also, e.g., U.S. Pat. No. 5,545,516 (Wagner) and U.S. Pat. Publ. 2001/0046662 A1 (Wagner et al.). Photodynamic therapy (PDT) has also been used as a treatment for several forms of cancer. PDT works by exposing a photosensitizing drug to specific wavelengths of light in the presence of oxygen. When this reaction occurs, the normally innocuous photosensitizing drug becomes cytotoxic via an activated species of oxygen, known as singlet oxygen. Some of these phototoxic agents can be given orally and are preferentially retained by tumor cells. PDT has been used effectively for ovarian cancer, lung cancer, breast cancer, esophogeal cancer, skin cancers and bladder cancers. However, because the effects of almost all PDT drugs are oxygen dependent, photosensitization typically does not occur in anoxic areas of tissue. For example, in vivo studies showed that induction of tissue hypoxia, by clamping, abolished the PDT effects of porphyrins (Gomer et al., Photochem. Photobiol., 40:435-439 (1984)).